Problem: Determine how many solutions exist for the system of equations. ${-8x-2y = -2}$ ${y = -4x+1}$
Solution: Convert both equations to slope-intercept form: ${-8x-2y = -2}$ $-8x{+8x} - 2y = -2{+8x}$ $-2y = -2+8x$ $y = 1-4x$ ${y = -4x+1}$ ${y = -4x+1}$ Just by looking at both equations in slope-intercept form, what can you determine? ${y = -4x+1}$ ${y = -4x+1}$ Both equations have the same slope and the same y-intercept, which means the lines would completely overlap. ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ Since any solution of ${-8x-2y = -2}$ is also a solution of ${y = -4x+1}$, there are infinitely many solutions.